Power hammer



Nov. 15, 1932.

Filed July 50. 1950 5 Sheets-Sheet 1 l/ I If 1 Ill 2| 3 w I '1 III i 618 L?()\ S d6 40 g L/ :36 I 6.2.

INVEN OR ATTORNEY Nov'. 15, 1932.

R. P. MARTIN POWER HAMMER Filed July 50, 1930 5 Sheets-Sheet 5 Patented Nov. 15, 1932 UNITED STATES PATENT OFFICE- ROBERT P. MARTIN, or SEATTLE, WASHINGTON, AssrGNoE or ONE-FOUBTHZTOV I HORACE BYFORD, or sEA'rTLE, w sHrNe-ron;

POWER HAMMER Application filed .Tu1y 30, 1930.; Serial No. 471,873;

My present invention relates to theart of power hammers andmore particularly to that class of power hammers which employ cen trifugal force to restore the hammer element 5 to its striking position after each blow has been struck, V

Considerable work has been done on power hammers of so-called portable size in an en dea-Vor to provide a power hammer which will be strictly portable, but which is more easily handled by one man, which will strike a blow sufliciently powerful as to do really serious work, such as demolition, breaking of concrete, etc., and whose striking mechanism 5 is so designed and arranged that long life with freedom from breakdowns may be ex pected from it.

A large number of hammers produced in the past have used striking elements which were pivotably secured to a rotatable hammer base and which were arranged to fold up within the hammer base on striking the tool. I have found that hammersso constructed,

which provided a positive engagement with r the hammer base, would transmit tothe hammer base, its driving gearing and its source of power a portion of the shock incidental to striking the blow. This has been found to be very harmful and hammers so constructed i have a very short useful life.

In my present design I have provided a hammer which is characterized by having its striking member or hammer proper slidably secured within a revolving hammer base. In this way I have found that the force of impact when the strikerengages the-tool is confined almost wholly to the striker itself, causing it to slide or reciprocate within the hammer base, and in this way I have the same effect as though the striking member were a freely falling body, and I have found that the gearing and driving means are not in any way affected by the shock of striking.

Having thus describedmy invention in brief, the objects I obtain with my device are,

namely:

First: The production of a power hammer which is characterized by extreme simplicity of construction of the striking member itself, a fact which permits economibodyat the time impactoccurs, 1

cal construction and long life for the tool.

Second: The production of a power hammer mechanism in which the striking member acts as though it were a freely falling Third The production of ahammer mechanism which is characterized by having a striking member or hammer which is so disposed within its rotatable hammer base that centrifugal force will act upon the strikerand restore it to itsstriking position after each successive blow. L Fourth: The production of a striking .mechanism for power hammers which admit .of providing "a relatively heavy striking member and which may be included within a hammer base of relatively small diameter. This enables the production of a heavy tool that will not be bulky or unwieldy.

Other and more specific objects will be apparent from the following description taken in connection with the accompanying drawings, wherein Figure 1 is a longitudinal sectional view through the central axis of my machine, 7

showing the same as driven by an electric motor. I e

Figure 2 is an elevation of my tool, certain parts being broken away to better show the construct-ion and relationship of the various parts. v I

Figures .3 and 4 are fragmentary sectional views showing my striking mechanism at different phases of its cycle of' operation. Referring to the drawingsthroughout which like referencecharacters indicate like .parts, numeral 10 designates the hammer 'eration of the machine.

necessity of employing a hammer baselO- of larger diameter, and addition it permits a larger mass ofmetal} disposed at-a; point where it is acted upon by the centrifugal *forces'to the greatest" extent and thus overcomes any tendency for the hammer to becomefrictionally engagedby the side wall SO-of the hammer base and prevented from being thrown out to itsfullest extent, which is requiredifor' proper engaging of the tool 32.

llhave found' 'some difficulty in thepast in so heat tre'at'ing an irregular shaped mass of metalso as toenable it to withstand the repeated impact without chipping. To overcome this condition I prefer to-insert into striker 18, by pressing securely thereinto, a

cylindrical tool engagin'gblock 34, which can bespecially heat-treated as animpacting surface. Inorder to prevent hammer 18 becoming air-boundwithin-cavity 20, Iprovide airports 36, and. also additional airducts 38,

on the hammer itself that the small cavity 40 may not'become air-bound.

I- believeit will be'apparent that any satisfactory driving means maybe-employed with my striking'mechanism. The arrangement I have shown has proven very'sat-isfactory and consists ofthe driven gear 42, idler gear 14,

which is adapted'to revolveupon the stubshaft 46, and the driving gear 18. Gear 48 is fixedly securedto the reVolvable-shaft 50 which inturn is suitably journaled on anti frictionbearings at 52 and 58. Inthe showingI have-made I have indicated an electric driving motor 56. In order toprovid'esuflicient electric power for serious work it is necessary tousea relatively highspeed motor. This keeps the weight to ajminimum but also; requiresa large reductionbetween the motor'shaft" and the hammer base. This condition is easily met by employing a driving 'w'orm'58j-anda driven wormgear 60, the latter-being fixedly securedto shaft 50. i

The electric'motor may be controlled in any", convenient manner as by the trigger switch 62, which is arranged to interrupt the electric currentsupplied over the feed wires 64; I'havefound it very convenient to' cover the operators hand-hold 66 with heavy liverub'ber; This prevents any danger ofelec-tric shock to the operator, and also cushi'ons'an-y Vibrations incidental'to theop- A' factor-that contributes-in a largedegree to-the' satisfactory operation of this machine is an adequate oiling system. In my design I have found it very desirable to use a rather thick oil in the worm cavity '68, Leakage from this chamber is prevented by the oil gland 70. In the gear chamber 72 I prefer to use a lubricating oil ofnormal consistency which should be varied from light in cold weather to heavy inwarm weather. v This I have found suiii'cient to: lubricate the gears themselves and by means of the oil chamber 74; and the cross openings 7 6 and 78 respectively, the oil from chamber 72 is led into the striker chamber-2.0. The anti-friction bearings at 1 1 and 16 are normally packed in light grease, and" oil retaining glands are'provided to retain the grease within the bearing chambers.

Method of operation In operating my device thefirst operation necessarily is to turn on the electric current by operation ofthe switch 62." This starts the motor and causes the hammer base 10 to revolve at relatively high speed. This will normally be, from 400' revolutions up, the 1.

higher speed being permissible as the hammers are made lighter. Let us assume-that a'blow hasbeen-delivered as shown in Figure 1, whereinthe striker, or more properly block" 34, has come in full engagement with I;

carrying the striking member is then free-to Z revolve past the tool. As soon as the striker has passed the tool centrifugal force begins to act upon themass of the striking member and quickly restores it to its extended or striking position-,ras indicated in Figure 4. The mechanism is now ready todeliver the next blow. v

The foregoing,description and the accompanying drawingsclearly disclose a preferred embodiment of my invention but it will be understood that this disclosure is'mer'ely illustrative and that such changes in the invention may be made as are fairly within the scope'and spirit of the following claims:

What I'claim-is: 1. In apower hammer, a tool; a revolvable shaft;,means for driving said shaft a hammer base fixedly securedto said revolvable shaft; an L-shaped hammer member having a body portion adapted for limited reciprocal movementv within and tangent to the circle of rotation of saidhanuner base; and. an L-shaped portion which extends at right angles to the body portion, toward the direction of travel of the hammer for substantial radial movement in and with respect to the plane of rotation of the hammer under the influence of centrifugal force developed by said base to move said body portion along its path of movement.

2. In a power hammer, a'tool; a revolv-- able shaft; a hammer base fixedly secured to said revolvable shaft; an L-shaped hammer member adapted to a limited reciprocal movement Within said hammer base; said L-shaped hammer having a body portion disposed to move on a tangent to the circle of V rotation of the hammer base and an L-shaped portion normal to the body portion and extending toward the direction of travel of the hammer and disposed in the plane of rotation of the hammer; the L-portion of said hammer so disposed that the centrifugal force created by revolving said hammer, will be largely directed along the longitudinal axis of the body portion of said hammer; a driving motor; a hand-hold; said tool, motor and hand-hold being co-axially disposed and reduction gear means connecting said motor and said revolvable shaft.

3. In a power hammer, a tool; a revolvable shaft; a hammer base fixedly secured to said revolvable shaft; an L-shaped hammer member adapted to a limited reciprocal movement within said hammer base; said L-shaped hammer having a body portion disposed to move on a tangent to the circle of rotation of the hammer base and an L-shaped portion which extends at right angles away from the body portion toward the direction of travel of the hammer and disposed in the plane of rotation of the hammer; the L-portion of said hammer so disposed that the centrifugal force created by revolving said hammer will be largely directed along the longitudinal axis of the body portion of said hammer; a block inserted into the working face of said hammer member, so disposed as to form a tool engaging surface; a driving motor; a hand-hold; said tool, motor and hand-hold being co-axially disposed and reduction gear means connecting said motor and said revolvable shaft.

In witness whereof, I have hereunto subscribed my name this 25th day of July ROBERT P. MARTIN. 

